Certain embodiments of the invention provide a method of promoting T lymphocyte proliferation, comprising contacting in vitro, ex vivo or in vivo a population of cells comprising T lymphocytes with an effective amount of N1-hexyl-N5-benzyl biguanide (HBB), or a pharmaceutically acceptable salt thereof, wherein contact with HBB, or a pharmaceutically acceptable salt thereof, causes proliferation of the T lymphocytes.
